1. Chemical characterization of the first stages of protoplanetary disk formation
Collaborators : Valentine Wakelam (supervisor)
Stéphane Guilloteau (supervisor)
Franck Hersant
Astrochemistry of Molecules and ORigins of planetary systems (AMOR)
Laboratoire d’Astrophysique de Bordeaux, France
Ugo Hincelin – 25th June 2010

2. Is there a link between interstellar matter & disk matter?
Introduction
Method
Results
Prospects
Disk formation
Is there a link between interstellar matter & disk matter?
Are initial conditions of disk formation important for the disk chemical composition?
Is thermal history of disk formation important?

3. <-- initial chemical composition of a diffuse cloud
Introduction
Method
Results
Prospects
Modelling steps
Steps: simulate chemistry during different phases (diffuse cloud  molecular cloud  disk)
How? using chemical gas-grain model Nautilus (Hersant et al. 2009, based on Herbst’s team)
<-- initial chemical composition of a diffuse cloud
T = 10K
n = cm-3
different ages
--> final chemical composition of molecular cloud = initial conditions for disk formation
T = f(time)
nH = f(time)
different evolution scenarios
--> chemical composition of the disk

4. density & temperature profiles
Introduction
Method
Results
Prospects
density & temperature profiles
Scenarios, from molecular cloud collapse to disk, extracted from hydrodynamic models (Visser et al. 2009…)
gas cell trajectory
arrival at 30AU from the protostar at 2.5x105 yr
R (AU)
z (AU)
(Visser et al. 2009)
temperature and density along trajectory = parameters for Nautilus

5. 3 models : testing the initial conditions
Introduction
Method
Results
Prospects
list of models
List of models used
3 models : testing the initial conditions
1 trajectory  evolution of T & n
different initial conditions for disk formation : varying the age of the molecular cloud
104
105
106 years old
2 models : testing the evolution ‘s impact of the temperature and the density
molecular cloud : 105 years old
1) 1 trajectory  evolution of T & n
2) no evolution of T & n
5 models : testing changes in thermal and density history
molecular cloud : 106 years old
temperature of the accretion shock (100K & 780K)
time of the shock (early & late)
temperature decreasing after the accretion shock

6. testing the initial conditions
Introduction
Method
Results
Prospects
testing the initial conditions
 Dependence of the disk chemical composition on initial conditions (age of parent cloud)
About one order of magnitude difference in the abundances of a lot of species when varying initial conditions
 Final chemical composition of the disk is influenced by the age of the parent cloud
Chemistry is not at equilibrium  time = important factor
H2CO = tracer of the age of the parent cloud?
Temperature and density evolution from Visser’s trajectory

7. testing the initial conditions – comparison with comets composition
Introduction
Method
Results
Prospects
testing the initial conditions – comparison with comets composition
- Similar abundances for some species (C2H2, H2CO…)
- Little CO on grain : disk temperature too high
- Lot of CO2 in 1 case : OH + CO  CO2 + H (efficient reaction)
(Bockelée-Morvan et al. 2004)

8. testing thermal and density history
Introduction
Method
Results
Prospects
testing thermal and density history
testing thermal and density history
model with evolution for T & n (Visser’s trajectory)
model without evolution for T & n
 thermal and density history of gas and dust changes the final chemical composition of the disk

9. testing changes in thermal and density history
Introduction
Method
Results
Prospects
testing changes in thermal and density history
parametric functions for the temperature and density profiles
maximal density
Shock
temperature
final temperature
Time of the transition
time of the shock
minimal density

10. CO abundance reproduced
Introduction
Method
Results
Prospects
testing changes in thermal and density history – temperature decreased at the end of the disk formation
use of Visser’s temperature profile with final decrease – cloud of 106yr
CO abundance reproduced
Results closer to comets composition (13/17 abundances reproduced within 1 order of magnitude)

11.  HCOOCH3, a tracer of temperature of the shock?
Introduction
Method
Results
Prospects
testing changes in thermal and density history – temperature of the shock
parametric functions – cloud of 106yr
 No big changes except for some species  good for identification of tracers
 HCOOCH3, a tracer of temperature of the shock?

12. testing changes in thermal and density history – time of the shock
Introduction
Method
Results
Prospects
testing changes in thermal and density history – time of the shock
parametric functions – cloud of 106yr
 Again no big changes except for some species  good for identification of tracers
 HC3N and C2H2, tracers of the shock of the time?

13. Test other trajectories and link parametric profiles with trajectories
Introduction
Method
Results
Prospects
Conclusion : Chemical composition of the disk is sensitive to the density and thermal history Some tracers would give us some information about the thermal history of the disk Chemical composition of comets seems to be a melting pot of matter from different locations in the disk (and envelope?)…
Prospects : Test variation on the temperature peak width  ongoing work Add a high temperature network in chemical model to better simulate warm regions
Test other trajectories and link parametric profiles with trajectories

14. Thank you for your attention
Introduction
Method
Results
Prospects
Conclusion : Chemical composition of the disk is sensitive to the density and thermal history Some tracers would give us some information about the thermal history of the disk Chemical composition of comets seems to be a melting pot of matter from different locations in the disk (and envelope?)…
Prospects : Test variation on the temperature peak width  ongoing work Add a high temperature network in chemical model to better simulate warm regions
Test other trajectories and link parametric profiles with trajectories
Thank you for your attention